In a wireless network, a user equipment (UE) may communicate with one or more radio network nodes (e.g., an eNodeB or eNB) to transmit and/or receive voice traffic, data traffic, control signals, and so on. The UE and radio network nodes may be capable of making radio measurements to in order to support various functionality, as further described below.
Radio measurements done by the UE may typically be performed on the serving as well as on neighbor cells over some known reference symbols or pilot sequences. Such measurements may be referred to as “UE measurements.” The measurements can be done on cells on an intra-frequency carrier, inter-frequency carrier(s) as well as on inter-radio access technology (inter-RAT) carriers(s) (depending upon the UE capability whether it supports that RAT). To enable inter-frequency and inter-RAT measurements for the UE requiring gaps, the network may configure the measurement gaps. As an example, during a gap, the UE may stop measuring a signal on a current cell, switch to a target cell to measure a signal on the target cell, and then come back to the current cell. Two periodic measurement gap patterns both with a measurement gap length of 6 ms are defined for LTE. Some measurements may also require the UE to measure the signals transmitted by the UE in the uplink.
The measurements are done for various purposes. Some example measurement purposes are: mobility, positioning, self-organizing network (SON), minimization of drive tests (MDT), operation and maintenance (O&M), network planning and optimization, etc. The measurements may be performed over a relatively long time duration on the order of a few 100 ms up to several seconds. The same measurements may be applicable in single carrier and carrier aggregation (CA). However, in carrier aggregation the measurement requirements may be different. For example the measurement period may be different in CA (e.g., it can be either more relaxed or more stringent depending upon whether the secondary component carrier, SCC, is activated or not). This may also depend upon the UE capability (e.g., whether a CA capable UE is able to perform measurement on SCC with or without gaps).
Examples of mobility measurements in LTE are cell identification (e.g., physical cell identifier, PCI, acquisition), reference symbol received power (RSRP), reference symbol received quality (RSRQ), and cell global identifier (CGI) acquisition. The mobility measurement may also comprise of identifying or detecting a cell, which may belong to LTE, HSPA, CDMA2000, GSM, etc. The cell detection comprises identifying at least the PCI and subsequently performing the signal measurement (e.g., RSRP) of the identified cell. The UE may also have to acquire the CGI of a cell. More specifically the system information (SI) is read by the UE to acquire the CGI, which uniquely identifies a cell, of the target cell. The UE may also be requested to acquire other information from the target cell, such as closed subscriber group (CSG) indicator, CSG proximity detection, etc.
Examples of UE positioning measurements in LTE are reference signal time difference (RSTD) and UE receive-transmit (RX-TX) time difference measurement. The UE RX-TX time difference measurement requires the UE to perform measurement on the downlink reference signal as well as on the uplink transmitted signals.
Example of other measurements which may be used for radio link maintenance, MDT, SON, or for other purposes are (1) control channel failure rate or quality estimate and (2) physical layer problem detection. Examples of control channel failure rate or quality estimate include paging channel failure rate and broadcast channel failure rate. Examples of physical layer problem detection include out of synchronization (out of sync) detection, in synchronization (in-sync) detection, radio link monitoring, and radio link failure determination or monitoring.
Channel state information (CSI) measurements performed by the UE are used by the network for scheduling, link adaptation, etc. Examples of CSI measurements are channel quality indicator (CQI), pre-coding matrix indicator (PMI), rank indicator (RI), etc. They may be performed on reference signals like common reference symbol (CRS), channel state information reference symbol (CSI-RS), or demodulation reference signal (DMRS).
The radio measurements performed by the UE are used by the UE for one or more radio operational tasks. Examples of such tasks are reporting the measurements to the network, which in turn may use them for various tasks. For example, in radio resource control (RRC) connected state the UE reports radio measurements to the serving node. In response to the reported UE measurements, the serving network node makes certain decisions, as an example, it may send mobility command to the UE for the purpose of cell change. Examples of cell change are handover, RRC connection re-establishment, RRC connection release with redirection, primary cell (PCell) change in CA, primary component carrier (PCC) change in PCC, etc. In idle or low activity state example of cell change is cell reselection. In another example, the UE may itself use the radio measurements for performing tasks, such as cell selection, cell reselection, etc.
In order to support different functions such as mobility (e.g., cell selection, handover, etc.), positioning a UE, link adaption, scheduling, load balancing, admission control, interference management, interference mitigation, etc., the radio network node may also perform radio measurements on signals transmitted and/or received by the radio network node. Such measurements may be referred to as “radio network node measurements.” Examples of such measurements are signal-to-noise ratio (SNR), signal-to-interference-plus-noise ratio (SINR), received interference power (RIP), block error ratio (BLER), propagation delay between UE and itself, transmit carrier power, transmit power of specific signals (e.g., Tx power of reference signals), positioning measurements, etc.
In general, communication between the UE and the radio network node may use duplex communication. A duplex communication system is a point-to-point system composed of two connected parties or devices that can communicate with one another in both directions. A half-duplex (HDX) system provides communication in both directions, but only one direction at a time (not simultaneously). A full-duplex (FDX), or sometimes referred to as a double-duplex system, allows communication in both directions, and, unlike half-duplex, allows this to happen simultaneously. Time-division duplexing (TDD) is the application of time-division multiplexing to separate outward and return signals (e.g., operating over a half-duplex communication link). Frequency-division duplexing (FDD) means that the transmitter and receiver operate at different carrier frequencies, typically separated by a frequency offset.
The LTE specification enables FDD and TDD operation modes. Additionally, half duplex operation is also specified, which is essentially FDD operation mode but with transmission and receptions not occurring simultaneously as in TDD. Half duplex mode has advantages with some frequency arrangements where the duplex filter may be unreasonable, resulting in high cost and/or high power consumption. Since carrier frequency number (evolved absolute radio frequency channel number/EARFCN) is unique, by knowing it, it is possible to determine the frequency band, which is either FDD or TDD. However, it may be more difficult to find difference between full duplex FDD and half-duplex FDD (HD-FDD) without explicit information because the same FDD band can be used as full FDD or HD-FDD.
In the 3rd Generation Partnership Project (3GPP), two radio frame structure types are currently supported: Type 1 (applicable to FDD, illustrated in FIG. 1) and Type 2 (applicable to TDD, illustrated in FIG. 2). Transmissions in multiple cells can be aggregated where up to four secondary cells can be used in addition to the primary cell. In case of multi-cell aggregation, the UE currently assumes the same frame structure is used in all the serving (primary and secondary) cells. The frame structure type 1 illustrated in FIG. 1 is applicable to both full duplex and half duplex FDD. For FDD, 10 subframes are available for downlink transmission and 10 subframes are available for uplink transmissions in each 10 ms interval. Uplink and downlink transmissions are separated in the frequency domain. In half-duplex FDD operation, the UE cannot transmit and receive at the same time while there are no such restrictions in full-duplex FDD. There is no need in guard period for full-duplex FDD. For half-duplex FDD operation, a guard period is created by the UE by not receiving the last part of a downlink subframe immediately preceding an uplink subframe from the same UE.
FIG. 3 is a table showing an example of uplink/downlink, UL/DL, TDD configurations defined so far in 3GPP. For each subframe in a radio frame, “D” denotes the subframe is reserved for downlink transmissions, “U” denotes the subframe is reserved for uplink transmissions, and “S” denotes a special subframe with the three fields downlink pilot time slot (DwPTS), TDD guard period (GP), and uplink pilot time slot (UpPTS). Choosing a specific UL/DL configuration may be determined, for example, by traffic demand in DL and/or UL and network capacity in DL and/or UL.
As shown in FIG. 3, subframes 0 and 5 and DwPTS are reserved for downlink transmission. UpPTS and the subframe immediately following the special subframe are reserved for uplink transmission. The length of DwPTS and UpPTS depends on the combination of DL and UL cyclic prefix lengths and on the special subframe configuration (10 pre-defined special subframe configurations are defined in TS 36.211). Typically, DwPTS is longer than UpPTS.
In case multiple cells are aggregated, the UE may assume that the guard period of the special subframe in the different cells have an overlap of at least 1456·Ts.
A UE may need to perform simultaneous transmission/reception in a TDD system in an inter-band scenario, an inter-frequency scenario, or an intra-frequency scenario:                Inter-band scenario, i.e., when an UL subframe/slot/UpPTS is configured in at least one cell on a carrier frequency in one band and a DL subframe/slot/DwPTS is configured in at least one cell on another carrier frequency in another band, wherein the UL and DL subframe/slot or other signals configured on different cells of different carriers in different bands at least partly overlap in time,        Inter-frequency scenario, i.e., when an UL subframe/slot/UpPTS is configured in at least one cell on one carrier frequency and a DL subframe/slot/DwPTS is configured in at least one cell on another carrier frequency, where the carrier frequencies belong to the same frequency band, wherein the UL and DL subframe/slot or other signals configured on different cells of different carriers in the same band at least partly overlap in time,        Intra-frequency scenario, i.e., when an UL subframe/slot/UpPTS is configured in one cell and a DL subframe/slot/DwPTS is configured in another cell on the same carrier frequency, wherein the UL and DL subframe/slot or other signals configured on different cells of the same carrier at least partly overlap in time,        
The different configurations may occur statically, semi-statically (e.g., with inter-band CA), or dynamically (e.g., with dynamic TDD).
The different carriers in the same or different bands mentioned in above scenarios may also belong to multicarrier configuration of the UE e.g., f1 and f2 may be PCC and SCC of the UE.
It may be resource and complexity demanding to require that all UEs are capable of simultaneous transmission and reception. Therefore, to address this issue for the inter-band scenario, 3GPP has specified the following UE capability in TS 36.331 (Rel-11).
BandCombinationParameters-V1130 :: = SEQUENCE {multipleTimingAdvance-r11ENUMERATED {supported}OPTIONAL,simultaneousRx-Tx-r11ENUMERATED {supported}OPTIONAL,bandParameterList-r11SEQUENCE (SIZE (1..maxSimultaneousBands−r10)) OFBandParameters-V1130OPTIONAL,...}
According to TS 36.331 (Rel-11), simultaneous Rx-Tx indicates whether the UE supports simultaneous reception and transmission on different bands for each band combination listed in supportedBandCombination. This field is only applicable for inter-band TDD carrier aggregation.
According to TS 36.306 (Rel-11), section 4.3.5.4, the simultaneous Rx-Tx field defines whether the UE supports simultaneous reception and transmission for inter-band TDD carrier aggregation.